The Unjust (2010)

A serial killer targeting elementary school students is on the loose. When the most probable suspect dies and the case looks like it's reached a dead end, police brass decide to create a killer - and anyone will do. Though Detective CHOI boasts an incredible number of arrests over his career his rank never showed it. Deciding this is his last chance for professional redemption, he makes a deal with JANG, who he has been investigating, and together they decide to set up an existing suspect as the murderer. The only hurdle in their plan is public prosecutor JOO, who takes on the case and who had been involved in a deal with rival construction contractor KIM. When secret deals and back alley agreements start to come to light, it only serves to drag all of them deeper and deeper into a dark hole of questionable ethics and abuse of the law.